Equipment for folding paper webs and the like

Apparatus for forming substantially parallel arcuate folds in a flat sheet of material, such as paper, moving along a sheet-feed plane, said apparatus comprising:

• two series of folding elements, each folding element having arcuate sheet-engagement means for forming a fold along an arc extending transversely to the direction of movement of the sheet between opposite edges of the sheet by engagement with a surface of the sheet along said arc,
• means supporting the folding elements for translational movement through a sheet folding zone along opposite sides of the sheet-feed plane with the folding elements of one series facing those of the other series across the sheet-feed plane in the folding zone such that their respective sheet-engagement means are substantially parallel to one another, and with the folding elements of one series alternating with the folding elements of the other series in the direction of movement through the folding zone, and
• means for causing the sheet-engagement means of the folding elements of one series to move relatively toward the folding elements of the other series in a direction substantially perpendicular to the sheet-feed plane so as to increasingly overlap the sheet-engagement means of the folding elements of the other series in such direction as the folding elements translate through the folding zone, such that the sheet-engagement means of the two series of folding elements engage opposite surfaces of the sheet, respectively, and progressively form substantially parallel arcuate folds in the sheet as said overlap increases as the folding elements translate through the folding zone.